1. Field of the Invention
This invention pertains to a fuzzy logic fault accommodation control system, and pertains more particularly to a gas turbomachine utilizing such a control.
2. Description of the Prior Art
In certain control systems the required reliability and safety of operation often requires that redundant sensors be utilized to sense the value of a parameter which is being utilized in the control system. For further reliability and/or safety of operation, such a control system may also include a predicted value for the operating parameter, often times dependent upon other operational parameters. In such a system the controller is therefore presented with three values of the parameter--the two sensed values and the synthesized value--and the control system must include discriminator criteria to determine which value to utilize for the parameter.
One application of such a control may be a gas turbine engine utilized for aircraft propulsion or the like. Here, efficient and reliable operation is paramount. Thus, a gas turbine will often include at least two sensors for sensing a critical control parameter such as the air pressure or the temperature at a certain location or station within the engine. Such a gas turbine engine controller typically includes a predetermined engine modeling scheme within the controller itself. The engine model continuously generates a synthesized signal, based upon prior experience, of what the value of the particular parameter being sensed is predicted to be.
Various arrangements have been offered in the prior art for discriminating or deciding which single value to use for the parameter. Some simplistic systems simply either choose one or the other of the sensed values, or may use the synthesized value instead of either sensed value in certain circumstances. Such a system is primarily concerned with accommodation of a faulty or failed sensor, and merely picks or chooses which one of the three values to be used. A far more sophisticated sensor fault accommodation discriminator is described in ASME paper 97-GT-222, "Model Based Fuzzy Logic Sensor Fault Accommodation", Healy et al, Jun. 2, 1997. Such arrangements as described in this paper require very large, accurate engine models and require large amounts of processor time and memory for implementation.